2009/04/06 06:48:15 42.303 13.383 8.3 3.00 Italy
USGS Felt map for this earthquake
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 06:48:15:0 42.30 13.38 8.3 3.0 Italy
Stations used:
IV.ARCI IV.ASSB IV.BSSO IV.CERA IV.CESI IV.MIDA IV.MTCE
IV.MURB IV.PIEI IV.SACS IV.SGG IV.TERO IV.TOLF IV.TRIV
IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.44e+20 dyne-cm
Mw = 3.25
Z = 5 km
Plane Strike Dip Rake
NP1 200 85 -35
NP2 293 55 -174
Principal Axes:
Axis Value Plunge Azimuth
T 9.44e+20 20 252
N 0.00e+00 55 13
P -9.44e+20 28 151
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.84e+20
Mxy 5.60e+20
Mxz 2.46e+20
Myy 5.78e+20
Myz -4.78e+20
Mzz -9.40e+19
--------------
-----------------#####
-------------------#########
-------------------###########
--------------------##############
----###########------###############
#####################-################
#####################------#############
####################----------##########
#####################------------#########
####################---------------#######
###################-----------------######
### #############-------------------####
## T ############---------------------##
## ###########-----------------------#
###############-----------------------
#############-----------------------
############----------- --------
#########------------ P ------
########------------ -----
####------------------
--------------
Global CMT Convention Moment Tensor:
R T P
-9.40e+19 2.46e+20 4.78e+20
2.46e+20 -4.84e+20 -5.60e+20
4.78e+20 -5.60e+20 5.78e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406064815/index.html
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STK = 200
DIP = 85
RAKE = -35
MW = 3.25
HS = 5.0
The waveform inversion is preferred.
The following compares this source inversion to others
USGS/SLU Moment Tensor Solution
ENS 2009/04/06 06:48:15:0 42.30 13.38 8.3 3.0 Italy
Stations used:
IV.ARCI IV.ASSB IV.BSSO IV.CERA IV.CESI IV.MIDA IV.MTCE
IV.MURB IV.PIEI IV.SACS IV.SGG IV.TERO IV.TOLF IV.TRIV
IV.VAGA
Filtering commands used:
hp c 0.02 n 3
lp c 0.10 n 3
Best Fitting Double Couple
Mo = 9.44e+20 dyne-cm
Mw = 3.25
Z = 5 km
Plane Strike Dip Rake
NP1 200 85 -35
NP2 293 55 -174
Principal Axes:
Axis Value Plunge Azimuth
T 9.44e+20 20 252
N 0.00e+00 55 13
P -9.44e+20 28 151
Moment Tensor: (dyne-cm)
Component Value
Mxx -4.84e+20
Mxy 5.60e+20
Mxz 2.46e+20
Myy 5.78e+20
Myz -4.78e+20
Mzz -9.40e+19
--------------
-----------------#####
-------------------#########
-------------------###########
--------------------##############
----###########------###############
#####################-################
#####################------#############
####################----------##########
#####################------------#########
####################---------------#######
###################-----------------######
### #############-------------------####
## T ############---------------------##
## ###########-----------------------#
###############-----------------------
#############-----------------------
############----------- --------
#########------------ P ------
########------------ -----
####------------------
--------------
Global CMT Convention Moment Tensor:
R T P
-9.40e+19 2.46e+20 4.78e+20
2.46e+20 -4.84e+20 -5.60e+20
4.78e+20 -5.60e+20 5.78e+20
Details of the solution is found at
http://www.eas.slu.edu/eqc/eqc_mt/MECH.IT/20090406064815/index.html
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The focal mechanism was determined using broadband seismic waveforms. The location of the event and the and stations used for the waveform inversion are shown in the next figure.
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The program wvfgrd96 was used with good traces observed at short distance to determine the focal mechanism, depth and seismic moment. This technique requires a high quality signal and well determined velocity model for the Green functions. To the extent that these are the quality data, this type of mechanism should be preferred over the radiation pattern technique which requires the separate step of defining the pressure and tension quadrants and the correct strike.
The observed and predicted traces are filtered using the following gsac commands:
hp c 0.02 n 3 lp c 0.10 n 3The results of this grid search from 0.5 to 19 km depth are as follow:
DEPTH STK DIP RAKE MW FIT
WVFGRD96 0.5 210 50 15 3.06 0.4004
WVFGRD96 1.0 205 70 20 3.05 0.4160
WVFGRD96 2.0 205 70 20 3.12 0.4420
WVFGRD96 3.0 200 75 -15 3.15 0.4405
WVFGRD96 4.0 200 75 -20 3.19 0.4534
WVFGRD96 5.0 200 85 -35 3.25 0.4598
WVFGRD96 6.0 200 85 -30 3.26 0.4573
WVFGRD96 7.0 200 80 -30 3.27 0.4525
WVFGRD96 8.0 205 85 -25 3.26 0.4457
WVFGRD96 9.0 205 85 -25 3.27 0.4367
WVFGRD96 10.0 205 85 25 3.29 0.4239
WVFGRD96 11.0 210 80 25 3.29 0.4136
WVFGRD96 12.0 210 80 25 3.30 0.4010
WVFGRD96 13.0 210 80 25 3.31 0.3864
WVFGRD96 14.0 210 80 25 3.32 0.3699
WVFGRD96 15.0 210 75 30 3.34 0.3524
WVFGRD96 16.0 210 75 30 3.34 0.3349
WVFGRD96 17.0 210 75 30 3.35 0.3179
WVFGRD96 18.0 210 75 30 3.35 0.3015
WVFGRD96 19.0 210 50 20 3.37 0.2893
WVFGRD96 20.0 210 50 20 3.37 0.2803
WVFGRD96 21.0 115 65 -5 3.38 0.2765
WVFGRD96 22.0 115 65 -10 3.39 0.2737
WVFGRD96 23.0 115 65 -10 3.40 0.2699
WVFGRD96 24.0 300 60 -10 3.39 0.2660
WVFGRD96 25.0 300 60 -10 3.40 0.2629
WVFGRD96 26.0 300 65 -5 3.42 0.2609
WVFGRD96 27.0 300 65 -5 3.43 0.2585
WVFGRD96 28.0 300 65 -5 3.44 0.2577
WVFGRD96 29.0 305 65 0 3.45 0.2583
The best solution is
WVFGRD96 5.0 200 85 -35 3.25 0.4598
The mechanism correspond to the best fit is
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The best fit as a function of depth is given in the following figure:
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The comparison of the observed and predicted waveforms is given in the next figure. The red traces are the observed and the blue are the predicted. Each observed-predicted component is plotted to the same scale and peak amplitudes are indicated by the numbers to the left of each trace. The number in black at the rightr of each predicted traces it the time shift required for maximum correlation between the observed and predicted traces. This time shift is required because the synthetics are not computed at exactly the same distance as the observed and because the velocity model used in the predictions may not be perfect. A positive time shift indicates that the prediction is too fast and should be delayed to match the observed trace (shift to the right in this figure). A negative value indicates that the prediction is too slow. The bandpass filter used in the processing and for the display was
hp c 0.02 n 3 lp c 0.10 n 3
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| Focal mechanism sensitivity at the preferred depth. The red color indicates a very good fit to thewavefroms. Each solution is plotted as a vector at a given value of strike and dip with the angle of the vector representing the rake angle, measured, with respect to the upward vertical (N) in the figure. |
The nnCIA used for the waveform synthetic seismograms and for the surface wave eigenfunctions and dispersion is as follows:
MODEL.01
C.It. A. Di Luzio et al Earth Plan Lettrs 280 (2009) 1-12 Fig 5. 7-8 MODEL/SURF3
ISOTROPIC
KGS
FLAT EARTH
1-D
CONSTANT VELOCITY
LINE08
LINE09
LINE10
LINE11
H(KM) VP(KM/S) VS(KM/S) RHO(GM/CC) QP QS ETAP ETAS FREFP FREFS
1.5000 3.7497 2.1436 2.2753 0.500E-02 0.100E-01 0.00 0.00 1.00 1.00
3.0000 4.9399 2.8210 2.4858 0.500E-02 0.100E-01 0.00 0.00 1.00 1.00
3.0000 6.0129 3.4336 2.7058 0.500E-02 0.100E-01 0.00 0.00 1.00 1.00
7.0000 5.5516 3.1475 2.6093 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00
15.0000 5.8805 3.3583 2.6770 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00
6.0000 7.1059 4.0081 3.0002 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00
8.0000 7.1000 3.9864 3.0120 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00
0.0000 7.9000 4.4036 3.2760 0.167E-02 0.333E-02 0.00 0.00 1.00 1.00
Here we tabulate the reasons for not using certain digital data sets
The following stations did not have a valid response files:
DATE=Sat May 2 09:11:35 CDT 2009